Our invention relates to improvements in a valve system of the kind shown in U.S. Pat. No. 4,938,097, issued to Stanley L. Pierce, which is assigned to the assignee of our present invention. Our invention includes features that are common to the invention described in U.S. Pat. No. 5,157,608, issued to B. G. Sankpal, J. A. Daubenmier, L. J. Kurdziel, J. F. Carnago, W. Lewis, Jr., and R. S. Williams. The '608 patent also is assigned to the assignee of the present invention.
The '608 patent describes a control system having a microprocessor that establishes optimum control pressure levels for fluid pressure operated clutches and brakes that are used to effect ratio changes, whereby optimum clutch and brake servo pressures are maintained for each ratio change as torque capacity of an off-going clutch or brake is reduced in synchronism with the increase in torque capacity of an oncoming clutch or brake.
Our invention includes also features that are common to the invention of U.S. Pat. No. 5,150,297, issued to J. A. Daubenmier, P. A. Baltusis, R. T. Cowen, J. E. El-Khoury, and R. S. Williams. The '297 patent also is assigned to the assignee of our present invention. It describes a valve system for controlling ratio shifts in a transmission control system that includes a microprocessor and that responds to sensed variables including engine speed, vehicle speed and driver actuated range selector position, thus enabling the control system to adjust to varying road speed, engine torque and road conditions with high quality shift performance.
The hydrokinetic torque converter of our invention has a bypass clutch controlled by the valve system. The bypass clutch has features that are common to the control system described in U.S. Pat. No. 5,029,087, (issued to R. T. Cowen, R. L. Huffmaster and P. K. Jain), and to the hydrokinetic torque converter control system of pending U.S. patent application Ser. No. 927,046, filed by B. J. Palansky, T. L. Greene, J. A. Daubenmier, G. F. McCall, L. H. Buch and P. E. Smith on Aug. 10, 1992. That copending patent application also is assigned to the assignee of our present invention. The disclosure of the co-pending application describes a torque converter control system having a lock-up clutch for establishing a controlled mechanical torque flow path between the engine and the transmission gearing and for modifying the bypass clutch capacity during shift intervals.